The importance of monitoring the physical condition of a fetus during the birth process is well established. Appropriate remedial action and/or intervention can then be used when indicated. In this regard, the pH of the fetus, as well as the fetal heart rate, are important indicators of fetal condition. Fetal monitoring equipment has been developed to obtain, analyze and display such information. Typically, such information is obtained from the fetus by means of a probe which is attached to the scalp of the fetus in utero and which remains in the scalp tissue throughout the birth process. An example of such a probe is shown in U.S. Pat. No. 4,658,825 to Hochberg et al, which is assigned to the same assignee as the present invention.
In order to obtain reliable information, particularly for pH, it is necessary that the end portion of the probe containing the pH sensor be securely positioned in the scalp of the fetus. This is sometimes difficult, since the clinician must accomplish the initial attachment of the probe by feel rather than by sight, and the resulting attachment must be sufficiently strong to withstand the movement of the fetus and the mother during the birth process.
Although the particular shape (spiral) of the needle shown and described in the '825 patent has proved to be significant in maintaining the secure attachment of the probe to the fetal scalp, the guidance of the probe to, and initial positioning of the probe on, the fetal scalp is also important, as well as the ability to rotate the probe so that the spiral needle moves into the fetal scalp while maintaining the probe body at an angle which is substantially normal to the scalp. This is often difficult to do under actual conditions.
For that reason, an insertion/placement tool is typically used with the probe to attach the probe to the scalp. While existing insertion tools are typically flexible to accommodate the insertion of the probe through the vagina and cervix of the woman in labor to the fetal scalp, flexibility alone does not result in proper initial placement and subsequent maintenance of the attachment of the probe to the fetal scalp. In order to accomplish reliable attachment, the applicant has discovered that the forward end of the probe must be initially positioned substantially normal to the fetal scalp, and must be maintained in that position by the insertion tool, while at the same time the tool must be rotatable from its far end (opposite from the near or fetal scalp end), with the far end of the tool being at a substantial angle relative to the near end which is at the fetal scalp.
Use of existing tools have resulted in difficulty in properly attaching the probe to the fetal scalp, which in turn often results in inaccurate or unreliable readings, particularly of pH.